A herbicide containing the compound A as an active ingredient is utilized in various applications since it can control various undesired weeds with a low dose. However, the compound A in the herbicide may decompose in some cases depending upon the conditions, and accordingly no desired herbicidal effects can be sufficiently achieved in some cases. Thus, various studies have been conducted on a method for suppressing decomposition of the compound A.
JP-A-9-143015 discloses a method for suppressing decomposition of the compound A in a granular herbicidal composition by using a dialkylsulfosuccinate or a benzoate. JP-A-2002-12509 discloses a method for suppressing decomposition of the compound A in a solid herbicidal composition by using a stabilizer such as boric anhydride, metaboric acid, quick lime, barium oxide, zeolite, calcium silicate, magnesium oxide or magnesium sulfate. JP-A-5-271021 discloses a method for suppressing decomposition of the compound A in a spray liquid having a herbicidal composition diluted with water by using inorganic magnesium salts.
However, these documents failed to disclose a method for suppressing decomposition of the compound A in a solid herbicidal composition by using a specific surfactant described hereinafter.